This invention relates to security systems wherein an alarm warning is transmitted to a remote site indicating unauthorized activities at a protected location. The alarm can be activated by unexpected sounds, motion of bodies, weight on the floor, etc. The alarm information may be transmitted to the remote monitoring site by use of private dedicated lines, radio circuits, or by standard dial telephone circuits. If a dial telephone circuit is used, an automatic dialer is used and such devices are equipped with recording devices for transmitting a message stating the location of the place originating the alarm.
The main problem experienced with such systems is the large false alarm rate. It is comparatively easy to make certain that unauthorized entry to the protected area is detected but it is most difficult to avoid false operation of the alarms. For example, in the case of sonic activated alarms it is most difficult to differentiate between quiet unauthorized activities and dogs barking, thunder, horn blowing, etc. The problem has reached such serious proportions as to lead to the introduction of legislation to prohibit the use of alarm devices transmitting to police and fire department telephone systems.
Sophisticated systems analyzing sounds so as to better distinguish between true alarms and false alarms have been developed. For example, techniques such as disclosed in U.S. patent No. Re.27,202 can be used for such service. However, the variety of sounds that can falsely operate alarms is so great as to make such procedures inadequate.